Water scarcity is the most severe constraint for agricultural growth in arid and semi-arid areas. To overcome this, there is a need to use the available water efficiently and economically which is an important strategy to address present and future water need. This study was conducted for two years in Misrak Azernet berbere Woreda starting 2017/18 to investigate the effect of defict irrigation levels on yield and water productivity on Onion. There experiment has nine treatments include: control (0 % DI); 20 % DI and 40 % DI level throughout growth stages; 0 % DI, 20 % DI, 40 % DI and 20 % DI (i.e: initial, developmental, mid and late stages) respectively; 40 % DI, 20 % DI, 0 % DI and 20 % DI (i.e: in initial, developmental, mid and late stages), respectively and 20 % DI at each growth stages (i.e: in initial, developmental, mid and late stages), respectively were laid out in RCBD replicated three times. The results indicated that DI levels in different growth stages had significantly affected the yield and yield component of Onion at (p â‰¤ 0.05). The highest marketable yield (29.32 ton/ha) was obtained from T1 (control treatment) whereas the treatment recieved 20 % DI level at late growth stage (T9) gave 29.14 ton/ha yield. The yield result from T1 had not significantly different with T9 (20 % DI at late growth stage). The lowest yield (15.23 ton/ha) was recorded from T3 which received 40 % DI throughout the growth stages. Water productivity (WP) was found different depending on water levels. The highest WP 9.9 kg/m3 was obtained from T2 (20 % DI throughout the growth stages) and has 1.95 kg/m3 greater than T1 (8 kg/m3). These results confirmed that with DI practies, it is possible to increase WP by saving water and increase income from scarce water. Therefore, it can be recommended that applying at 20 % DI of CWR at late growth stage (T9) in 4 days irrigation interval is beneficial for obtaining optimum Onion yield and increases WP that brings higher economic return under scarce water condition. The farmers in scarce water resource area could also be used T2 (20 % DI of CWR throughout growth stages) as option to save more water.
Keywords: Bulb yield, Deficit irrigation, Evapotranspiration, Growth stage and Water Productivity.